Every public tweet ever posted, since March 2006 when Twitter began, will be archived by the US Congress. Whether it be the first tweet by co-founder Jack Dorsey or Conan O'Brien's tweet announcing his surprise following of Sarah Killen, all publicly posted tweets will be included within the archive.

Twitter and the Library of Congress both announced the decision on their blogs. Twitter boasts of having over 55 million tweets posted on their service each day. The Library of Congress will be available to use the tweets six months after they are posted for "internal library use, for non-commercial research, public display by the library and preservation".

Twitter's general counsel Alex MacGillivray spoke to the BBC regarding the announcement, "I think it shows the tweets are an interesting part of the historical record. It is not something we imagined when we were forming the service."

Twitter in the past and continues to allow its users to instantly publish breaking news and have public comment immediately. Matt Raymond's Library of Congress blog post speculated that the collection of tweets could have some positive effects for research of social behaviour. "I'm no Ph.D., but it boggles my mind to think what we might be able to learn about ourselves and the world around us."

The Library of Congress already stores over 167 terabytes of web-based information with tweets being the latest edition to the large collection of material.